How SSRIs work - Diagram
Serotonin is released by certain neurons in the brain. It is released by the presynaptic neurons and travels across a synapse. The neurotransmitter chemically conveys the signal from the presynaptic neuron to the postsynaptic neuron and then it is reabsorbed by the presynaptic neuron where it is broken down and reused. By preventing the re-absorption and breakdown of serotonin SSRIs effectively increaseits levelsin the synapse and thus continue to stimulate the post synaptic neuron. This compensates for whatever is wrong with the serotonin system in OCD.